The present invention relates generally to fluid pumps, and, more specifically, to a pump configured for pumping blood in a living body.
Although significant progress has been made over the last two decades to develop implantable left ventricular assist devices and artificial hearts, two significant problems still remain. These problems are long-term hemocompatibility and mechanical reliability.
The hemocompatibility problem is universally due to the use of polymeric or rubber pumping ventricles that are prone to eventual thrombogenesis, clotting, calcification, etc. They are not yet suitable for reliable, long-term pumping. In addition, flex life is a concern. With regard to mechanical robustness and reliability, it has taken decades of improvement to attain a relatively low level of reliability compared to what is needed. This mechanical problem is due to the fact that all approaches are too complex. They involve many moving parts, they use ball bearings and other bearings prone to wear, fatigue, and shock, incorporated are springs, linkages, etc. Whatever the basic approach, they have all been prone to wear and friction. Some use mechanical pusher plates and some hydraulically actuated rubber ventricles.
Low mechanical reliability of the Total Artificial Heart (TAH) is supported by the "cause of termination" in Table 1, which compares the life records of four leading total artificial heart programs. The table is taken from the recently published NHLBI document entitled, "Report of the Workshop on the Artificial Heart." The table is found on Page 36 of the workshop in a paper written by well-known William S. Pierce, M.D., Professor of Surgery, Hershey Medical Center, entitled, "Overview of Mechanical Circulatory Support Program."
As can be seen, implanted pumps have lasted up to 160 days, and in all three long term cases, the cause of termination was mechanical failure.
At the end of his paper, Dr. Pierce states that further research and development is required in the areas of long-term reliability and in the development of better polymeric materials. This applies to left ventricular assist devices as well. The following recommendations are excerpted from his paper.